Wait ... he slid under her ... but face down 😞 missed opportunity. (Assuming she was OK with it, of course)
@liesjeversteven What do you mean this happens all the time at festivals in Europe? The mud slide under the woman peeing?

For me, I like sitting, especially at home. BUT, my favourite bathroom was my uncle's. He had a house with a custom built bathroom. It had a sink, 4 person shower, urinal, commode and a bidet. This was upstairs. There were no doors on the bathroom and it was mostly visible from the office/guest bedroom #2. I loved it because any female who stayed upstairs would go into the bathroom and I could see them shave, shower, pee ... everything. The first time it happened, I thought my uncle and his girlfriend were going to be upset that I woke up and saw her.
Nope. She didn't care. As long as I didn't get creepy or stalk her, it was natural. My uncle was OK with it as well. I miss that house....

This is only one of my weirdest ... I had one kind of like Sabuto. But I had a hard on and had to pee. So I went into the bathroom and could not push my erection down to the toilet. It was going to be in my face, if I let go. My (shared) apartment had no shower and the tub would take too long to fill.
I ended up lying on the floor with my head beside the base of the toilet and holding my back up with my hands. I hoped I was aiming at the bowl. Then the boor opened and my housemate, D, came in. She asked what was I doing and started laughing.
I was embarrassed and told her. She braced my back and pointed me at the bowl and I peed in the toilet. She let me down (mostly easily) and then sat down and peed while I was still on the floor. I do not know how I did not orgasm right then. She finished and left the bathroom.
I got up, washed my hands, and went to my room to relieve my really painful erection.

A lot of what I do after depends on where I am, how much privacy I have, and if the clothing I am wearing is at the end of its usefulness. I get a lot of mileage from old T-shirts and underwear and wear them until the elastic wears through the underwear.
With those types of underwear:
1, If I am at home and have time, I jump into the shower and shower off as much as I can, discarding the underwear.
2. If I am at a public place, I bin the underwear.
Once I soiled my pants and underpants (yes, it was "C" restaurant ... and it was about a year before I heard anyone else mention it.). Luckily, I had a long T-shirt (promo 4XXXX) and wore that home. I was literally shaking that I would get pulled over and have to explain why I had no clothes on under a huge shirt.

I may have always known, but the first time I noticed ....
My cousin (and best friend / surrogate older sister at the time) and I had always bathed / showered together. She is one year older. One day we were at home and had gotten filthy playing in the garden with the sprinkler. Before we could go into the house, we showered in the basement / mudroom/ laundry floor shower (just a shower head over a drain in the middle of the floor), we had to shower off in our bathing suits. As we scrubbed ourselves with soap from head to toe, I passed her the bar and it brushed across her bikini bottoms. I had soap in my eyes. She kind of moaned. I was clueless as to what happened, she asked me to kneel and I did.
I think I shared the story here a long tine ago. But I got to see her pee from VERY close up. It is probably the start of my interest in all things Omo.

My wife and daughter both have complex medical issues and luckily they are under control at this time. I am glad your son doesn't need surgery. There been there many times where I could not give a lot back to this community when I wanted to do so.
Just do what you can, when you can and take care of your family and yourself first. Whatever you can share is appreciated.

Personally, I think it depends on the context and how it is handled.
Examples:
Having a non-human with similar reaction(s) (embarrassment, sexual gratification, bodily function, etc.) to a human may give empathy/insight into the character.
Having similar "equipment" (but possibly for different purposes) may cause some story tension and relief. (pun intended).
Having a completely different biological process system could make for a symbiosis (start with humans breathing out CO2 and plants taking in CO2 and producing O2 as a simplistic concept) could make an interesting story, but may be a lot of work,
These are off the top of my head thoughts. I say go for it and see how it feels. If YOU like the characters and can put into words how they feel, I think that there are people who will be able to feel that in your writing.

My wife is not into anything Omo, but she has always announced when she has had to pee.
My heart still immediately races when we are driving and have to stop at a non standard place (corner of a mall parking lot, side of a highway, etc.) and she pees a waterfall. She knows of my interest, and to her credit she peed on my hand once, but it did nothing to turn her on at all, but she still mentions it and seems to wait until the last second to go whenever she has to go.

I will try
She looks into my eyes and presses herself into me, her legs straddling my leg. She presses herself against me, lips slowly trailing up my cheek to my earlobe.
She quietly says "I need to go very, very badly ...." as she takes the lobe between her lips and sighs while her hands pull me into her embrace.
She leans me on my back and rolls onto my body. Her hips kissing my hips. Her body pins me to the floor. She leans up, letting my ear go with a soft, moist 'pop'.
"I need to hear it..." she asks. Her eyes are searching mine.
I am so aroused I can't speak. All the water has deserted my mouth. She is a rainstorm about to burst and I am a drought of words.
"I ... am ... so ... full ..." she pleads. I am not trying to be mean. I am speechless. It is as if I have been granted a wish and am overawed. I move my dry lips.
A tear slides down her nose and impacts my cheek, breaking my enchantment.
"No ... I mean Yes... Please, Yes! Please ..." I chatter like a flashflood.
Her eyes close and the universe pauses between our breaths.
We explode.

I guess that may be why you are feeling it then. I hope that when you can wet you can reduce your stress when it happens. If you can't do that already, maybe try to visualize your stress leaking out when you wet.
We are all here with you and DO understand, I hope you know.
Thank you for sharing with us.